Method for producing fibrous cellulose from plant stalks and utilization of such fibrous cellulose



Y as the cellulose fibre that was sought after.

Patented Dec. 22, 1936 I STATES PATENT OFFICE George A. Low and Jim'ArGrant, New York, N. Y.,'assignors to Martin Hill Ittner, Jersey City, N. J. I

No Drawing.

Application June 22, 1934,

Seriai No. 731,840

24.0iaims. (Cl. 92-14) Our invention is more particularly applicable to the production of fibrous cellulose from flax straw, although it is also applicable to other fibre-bearing plant stalks, as for instance hemp, jute, ramie and other bast fibres, and relates not only to the production of such fibrous cellulose but also to the utilization of said fibrous cellulose in making products such as paper, yarn and fabrics made of yarn or thread.

Heretofore iiax fibre has been produced from fiax straw only by means of a number of laborious, wasteful and expensive operations. Flax straw contains in the neighborhood of ten to fifteen per centum of fibrous cellulose and approximately 90 to 85--per centum of non-fibrous, non-cellulose woody matter. The customary method of obtaining the fibre from the straw is to subject. the whole straw to a retting or rotting process that depends upon fermentation and bacterial action for the partial disintegration of the woody non-cellulose part of the straw, which retting when properly controlled has a less degenerative action on the fibrous cellulose itself than on the woody material. The whole, process is wasteful for the following reasons: All the woody non-fibrous material is rendered worthless and unutilizable as it is subjected to a partial retting or rotting, an excessive amount of labor for handling is necessary, and as the woody matter is not completely removed it is necessary to hackle the fibre thus obtained by combing it through banks of needles which while removing much npnfibrous material also causes avery considerable loss of good fibre in the form of tow of low value. Although the process of hackling that has heretofore always been necessary in preparing flax fibre removes the greater part of the rotted nonfibrous matter, some of this material known as shives almost always remains adhering to the fibres and is largely responsible for the unevenness generally observable in linen threads and fabrics. For years people interested in the production or fiax fibre have sought chemical methods for the extraction of the fibre from the woody nonfibrous material to replace the expensive retting process. I All of these methods have been subject to the disadvantages that the woody non-fibrous material, sought to be removed, was present in amount ranging from seven toten times as great This being the case, a prohibitive amount of chemical has been required per unit of fibre obtained and the quantity of material subjected to chemical treatment was necessarily so large; from eight to eleven times the amount of fibre obtained, that the output -of such a treating plant would be small and the operation uneconomical. Furthermore all chemical processes have heretofore resulted in rendering the non-fibrous woody material unavailable for useful purposes.

The principal objects of the present invention are to provide novel and advantageous methods of obtaining fibrous cellulose from the aforesaid plant stalks and also methods which go further and utilize the fibrous cellulose in the making of finished products such as paper, thread, yarn and fabrics made from said yarn.

In carrying, out our invention we have, in contrast with the old, wasteful and expensive processes that have been proposed up to the present, devised a treatment partly physical and partly chemical whereby we readily separate mechanically from seventy to seventy-five per centum of the non-fibrous material without change or deterioration of its chemical character thereby ob- ,taining a crude fibre comprising substantially equal proportions of fibrous and non-fibrous material, and extract the cellulose fibre therefrom in a substantially pure condition by chemical means, all without injury to the fibre. It will thus be seen that by our treatment only a relatively small amount of woody material, say about one-seventh to one-tenth as much as heretofore, must be acted on by chemicals as compared with the amount acted upon in any process that subjects the whole straw to a chemical or fermentation process. By our process the non-fibrous material at least to the extent of from 70 per centum to '75 per centum of the straw, can be removed without deterioration and will be suitable for use in cattle feed, whereas former processes have destroyed or degraded and wasted the non-fibrous portion of the straw. The simple and novel mechanical operation of separating from unretted straw this non-fibrous material and the crude fibre, that forms part of our process, can be performed with ease on the farm where the straw is grown thus leaving the'nonfibrous material, which is valuable for cattle feed, on the farm where it can be utilized and eventually got back to the soil as manure without exhausting or depleting the soil. The crude fibre thus obtained and constituting only about 25 to 30 per centum of the straw can then be baled and shipped to the chemical treating plant at a saving of freight over the cost of transporting the whole straw.

In the operation of separating from the woody material the crude fibre described above we may use a scutching machine as for instance that described in U. S. Patent No. 1,950,403.

A scutching operation for obtaining such crude fibre has been referred to in the process described in U. S. Patent No. 1,837,228. The process described in this patent differs from the present invention in the fact that it furnishes a means for extracting with the aid of certain solvents some of the gums and soluble impurities that interfere with spinning the fibres thus obtained, and that it is substantially physical in each operation, such operations including scutching the straw, extraction of the crude fibre with a solvent exerting physical action, and hackling of the extracted fibre for removal of shives, the shives not being soluble in thesolvents employed.

Our present process involves both physical and chemical operations, these being the mechanical scutching of the straw to obtain the crude fibre, and a chemical treatment which digests and completely removes the'remaining woody material or shives and gums, leaving substantially pure fibrous cellulose uninjured by the treatments.

We subject the crude fibre obtained by scutching untreated fiax straw to an extraction with hot water preferably near the boiling point. This removes approximately one third of the nonfibrous material. This water digestion is very rapid and is hastened by stirring or agitation or the circulation of the water through the fibre. It is desirable to keep the fibre submerged and not to beat air into the water unnecessarily, so that oxidation may be minimized. Even at this stage, the fibre when dried may be used to form yarn by the usual flax spinning operation. Preferably, however, we remove the water from the fibre quickly and then subject the fibre to a further treatment with caustic alkali, such as caustic soda of approximately 10 per centum strength, and corresponding approximately to 14.6 degrees Baum. In treating the fibre with liquids it is desirable to run the liquid in through the bottom of the tank so that it may the more readily displace air. soda treatment in a closed tank or kier that will stand with safety an internal working gage pressure of, for example, 140 pounds per square inch. The pressure tank is filled with fibre and liquid so as to completely displace air from the vessel. A suitable raised expansion tank, also capable of withstanding pressure, is provided and attached to the kier to provide room for the expansion of the caustic soda solution with increased temperatures and to insure against entrance of air into the kier with dropping temperatures and corresponding contraction of the caustic soda solution. Suitable circulation of the liquid in the pressure tank or apparatus may be obtained in any suitable manner, as by pumping the liquid through the tank- (preferably back and forth alternately) or by use of a pulsating device to cause a back and forth movement of the liquid through the fibre. A suitable means is provided for heating the contents of the kier, as for instance by the use of a steam jacket, or steam coils, or an outside heater.

We have found that caustic soda solution of approximately 10% strength when heated to a temperature of from 320 F. to 360 F. rapidly digests the shives and other non-cellulose matter completely leaving substantially pure cellulose uninjured by thetreatment. v

In specifying strength of alkali, working temperatures and pressures we are merely indicating good working conditions but do not wishto be We-prefer to perform this caustic confined too closely to the figures given. Thus, we have operated with varying strength of caustic soda other than 10%. We have employed strengths up to and exceeding 20% caustic soda. Althoughthe higher concentrations digest the woody matter somewhat more rapidly, they are likely to exercise some deleterious action on the fibre itself, and a further objection to the use of the higher concentrations is to be found in their greater cost. We have also tried lesser concentrations than 10% caustic soda but with the other conditions the same their efiiciency is quite appreciably less and the time necessary for treatment is extended, and, if the concentration is much less than 10%, the removal of shives is incomplete. Probably, any economy that is sought after by the employment of alkali solution much less than 10% is lost by the greater time of treatment required and by incomplete removal of shives, as well as by injury that comes to the fibre through unnecessarily protracted treatment. I 7

Although we have specified the preferred temperature range, we have operated above and below the limits given. Apparently an increase in temperature much above 360 F. is less advantageous than the preferred range, due to possible injury to the fibre at higher temperatures. Furthermore, operation at temperatures much below 320 F. requiresprotracted treatment to remove the shives and is distinctly less advantageous than operation in the preferred range.

Preferably we continue the digestion in the 10% caustic solution for three hours at the temperature range specified. Under the conditions specified most of the shives have disappeared in two hours time but to insure their complete removal we digest as specified for three hours. We have found that the length of time of treatment can be reasonably extended without injury and are thus assured that the conditions given, though desirable, can be varied within tolerances that can readily be met.

After subjecting the fibre to the preliminary hot water extraction we sometimes give the fibre an extraction with hot sodic carbonate solution before treating with caustic soda. Various strengths of sodic carbonate or soda ash solution may be used but we found it advantageous to employ a strength of approximately 3% to 5%. The soda extracts much of the material not completely and not readily extractible with hot water but does not destroy or remove the shives which are later removed in the aforesaid treatment with 10% caustic soda.

We are aware of the fact that varying strengths of caustic soda have'been used in some of the processes for preparing fibrous cellulose, notably in the soda process for making paper pulp from wood. The processes heretofore in use employing caustic soda'in the preparation of fibrous cellulose are substantially different from our process and are incapable of making fibre from fiax and have never been successfully employed for this purpose. In the preparation of wood pulp for paper caustic soda as strong as'8 to 10 degrees Baum, or from about 5.2% to 6.58% caustic soda, is employed at first for a short time in the cook, but, as the method of heating employed is to blow'live steam into the liquor and wood chips, the caustic soda liquor becomes rapidly diluted to five per cent and. lower before the temperature of the boiling point of water is reached. The time necessary for digesting wood pulp with the dilute caustic soda employed is ordinarilyv eight to ten hours. This treatment is not sufiicient to completely destroy and remove the non-cellulose material in wood pulp. Knots and bark are screened out after the digestion with the dilute caustic soda and it is necessary to employ a considerable amount of bleach to remove the non-cellulose material not removed by the dilute caustic soda treatment and by screening.

A further important difierence in the production of fibre from wood and other fibre bearing materials as compared with our process is that in these former processes all the non-fibrous material is subjected along with the fibrous to the chemical treatment whereas in our process substantially six-sevenths of the non-fibrous material is, removed mechanically before resorting to digestion and chemical treatment thus greatly facilitating the production of pure fibre.

Dilute caustic soda has also been employed in cleaning rags in low pressure, low temperature cooking preparatory to making into paper. Concentrated caustic alkali solutions have been used for short time treatments at comparatively low temperatures inmercerizing fibres but no one has previously employed caustic soda under the conditions of concentration, temperature and time that we recommend either for the removal of shives from fiax fibres or on other'fibres. On the other hand we have prepared by our process fiax fibre that is cleaner, stronger and whiter than any unbleached fibre we have ever seen prepared by other processes.

Our process employs in its preferred form caus-.

tic soda solution of suitable concentration to digestaa'nd remove shives and woody material from crude fibre under the conditions of time, temperature and pressure employed, without injury to the cellulose fibres, the action of the caustic soda solution being a selective chemical action. The concentrations of caustic soda solutions heretofore used as in the digestion of wood chips for the making of wood pulp have not been sufiiciently strong, and the temperature and pressures as heretofore used have not been sufficiently high and prolonged to get proper benefit from the selective chemical action of caustic soda such as we obtain in suitable concentrations, used under suitable conditions or time and temperature. for the preparation of cellulose fibres have had to depend largely, for the removal of woody noncellulose material, on chlorine bleaches which although they act more strongly on non-cellulose impurities than on cellulose fibres, nevertheless exert a very appreciable injurious action on pure cellulose and'therefore can not be classed with caustic soda, under recommended conditions of concentration, timeand temperature, as a chemical having a distinctly selective preference for non-cellulose impurities. There are, however, other chemicals which act under suitable conditions selectively against non-cellulose impurities without acting-prejudicially against purecellulose. other fibre-bearing stalks be subjected to somewhathigher concentrations of the chemicals ordinarily employed in the sulphite paper process, or of those used in the so-called sulphate 7 paper process, and under .conditions of tempera- For this reason processes heretofore used I Thus, if crude fibre derived from fiax or obtained from caustic soda under the conditions given, but different to some degree in their chemwhereby these impurities may be substantiallyremoved, without, however, exerting a harmful action on the cellulose fibres, thereby producing substantially pure fibrous cellulose.

After subjecting crude fiax fibre, as already dekali or other selective chemical is removed and the fibre is subjected to washing with water and a clean, strong, light colored fibre is obtained free from shives and gummy matter, being substantially pure cellulose, with substantially'no loss or deterioration of actual cellulose.

When we wish to make our fibre into paper, the fibre made after the manner which We have described may be taken without drying and subjected to the various mechanical processes com monly in use in paper mills.

Linen paper as heretofore. made has had its origin in rags and other waste material of uncertain supply which must be subjected to various 'mechanical and chemical treatments in order to produce a satisfactory article. Our process had produced the highest grade linen paper from clean flax straw and our method compares most favorably both from a sanitary point of view as well as in quality of product with linen made from rags. A further advantage characteristic to our process is that owing to the efficient removal of non-cellulose matter very much less chlorine bleach is required in bleaching than is required in making paper from ordinary rag stock thus producing less deterioration of the cellulose fibre, as chlorine bleaches are destructive in proportion to the amounts that must be used.

The cellulose fibre after being thoroughly degummed and deshived according to the presentinvention is particularly suitable for use not only for the manufacture of high grade paper but for other purposes including the manufac ture of high grade threads and yarn whether made by spinning or in other ways. The high grade cellulose made by our process may be 'used in the manufacture of rayon, gun cotton, cellophane and other products. Obviously if it is unnecessary to have products of such high quality the degumming and deshiving operation may not be carried out so completely and thoroughly.

A very important advantage realizable from the present invention is that the fibre made as described after cutting to suitable lengths is found to be capable of easily spinning as 100% fiax fibre on either cotton or woolen machinery. When out in about 3 inch lengths it works well on cotton spinning machinery, and in lengths of about 6 to 8 inches it works well on woolen machinery and in uncut lengths, it works well on linen machinery. An important reason for our fibre working so easily on either cotton or woolen machinery is that the fibres which we produce are so free from non-fibrous impurities and gums that during the spinning process the ultimate fibres not being held together by gum, as is commonly the case with flax fibres, slip easily on one another and thus assume an even overlappmg position with respect to one 75 scribed, to our digestion process the caustic alful influence at raised temperatures.

another thus furthering the ease of the spinning operation.

According to a modification of our process in the preparation of flax fibre for making linen fabrics we obtain advantageous results, both with regard to quality of fibre obtained and cost of production. In employing this modified process, we scutch the untreated straw or plant stalks for the production of a crude fibre as already described. For making fibre for linen manufacture we prefer to take the scutched fibre, as it comes from the scutching machine, and place it in loose hanks or bunches in the apparatus or in rolls in order the more readily to shake out the material later into long handfuls of straight fibres. The loose hanksof crude fibre are put into the digesting apparatus and digested with hot water which should completely cover the fibres in order to exclude air which has a harm- We then subject the fibre to digestion and extraction with hot water forthe removal of water soluble nonfibrous matter. Although any degree of heat not involving excessive temperature and pressures is favorable for the digestion of the nonfibrous impurities, we find that the effectiveness ofthe digestion and the removal of soluble nonfibrous impurities is increased by the use of pressures and temperatures above the atmospheric boiling point of water. The effectiveness of the digestion of this modified process, the more complete penetration therein of the non-cellulose woody material of the crude fibre by the high temperature water, and the lack of solvent action on the fibre-coating waxes are features which assist in differentiating between our modified process and the process covered by'U. S. Patent 1,837,228. Although we find that any. degree of hot water is somewhat favorable to the digestion and water extraction of soluble nonfibrous matter; we also find that the efficiency of the digestion and extraction is at a maximum when carried out with water under pressure at a temperature of between 320 F. and 360 F. Crude fiax fibre treated in this way and digested for two hours or more is equal to or better than the best fibre produced by the customary retting methods. Although after either such hot water treatment or the customary retting the shives remain and must be removed by-hackling, the fibres are about equally ready for making into linen fabrics.

We have also found that as a modified process especially for use in making linen fabrics we can subject the fibre to a sodic carbonate digestion either with or following the hot water digestion described. A desirable concentration of sodic carbonate solution is approximately 5%.

although diluter .and stronger solutions have been used. The shives are not completely removed by either hot water or sodic carbonate solution and the remaining shives may beremoved by hackling. The non-fibrousmaterial is not, however, so completely removed with water or sodic carbonate solution as under the treatment which we have described with the use of caustic soda.

In both of the modified methods described above the extracting liquid, hot water in one case and hot sodiccarbonate solution in the other, may be used at any "temperature and corresponding pressure up to 360 F. This latter temperature may even be exceeded somewhat .if air is carefully excluded from the apparatus though there is no advantage in working at a higher temperature than 360 F.

We have also discovered that the production of fibrous cellulose is facilitated by the use of following digestion. The action of these wettingout agents in conjunction with our process is twofold. First it causes the liquor to penetrate the fibres quickly so that the subsequent digestions are hastened, and secondly when used in connection with the washes following digestion objectionable foreign mineral impurities, particularly iron compounds which cause discoloration, are thereby removed or prevented from entering the fibres. We have found that for our particular purpose open chain compounds having a terminal linkage consisting either of a monovalent salt of a sulphate, or of a salt of a sulphonic acid are very desirable, and we have found the sodium salts to be the best. One of these compounds that has given particularly good results is known as Syntex T. and is the sodium salt of a terminal sulphonicacid group attached to an dpen chain organic body and is valuable both for its rapid removal or prevention of objectionable iron discolorations invthe fibres.

It should be understood that various changes may be'made in the process and that various features may be used without others without de-- parting from the true scope and spirit of the invention.

Having thus described our invention, we claim:

1. In the preparation of flax fibre, the scutching of unretted flax straw to obtain crude fibre, and the digestion of the unhackled unretted crude fibre so made with substantially ten per centum caustic soda at a temperature of from 320 F. to 360 F. for the chemical removal of non-cellulose material including shives.

2. In the preparation of fiax fibre, the scutching of unretted flax straw for the mechanical removal of the seventy per centum to seventy-five F. under pressure, for the chemical removal of woody non-cellulose material.

3. In the preparation of flax fibre,.the scutching of unretted flax straw to obtain crude fibre,

the digestion of the unhackled unretted crude.

fibre so made with substantially ten per centum caustic soda at a temperature of from 320 F. to 360 F. for the chemical removal of non-cellulose material including shives, the washing of the fibre with water for removal of soluble alkaline material, and the drying of the fibre preparatory to spinning.

4. In the preparation of flax fibre, the scutching of unretted fiax straw for the mechanical removal of the seventy per centum to seventyfive per centum of non-fibrous material from the thirty per centum to twenty-five per centum of crude fibre, the digestion of the unhackled unretted crude fibre'thus obtained with caustic.

soda in excess of eight per centum strength for three hours at at emperature in excess of 315 F.,

, under pressure, for the chemical removal of 5. In the manufacture of fibre for paper- (5 J stalks for the production of retted crude fibre so obtained making, the scutching of unretted flax straw to obtain a crude fibre, the digestion of the unhackled unretted crude fibre so obtained with alkaline reagents and with the aid of heat for the chemical removal of non-fibrous impurities, and the washing of the fibre for the removal of soluble impurities.

6. In the manufacture of fibrous cellulose, the scutching of unretted flax straw to obtain crude fibre, and the digestion of the unhackled unwith a chemical having a selective chemical dissolving action on the non-cellulose matter in the unhackled crude fibre and with the aid of heat and pressure to facilitate chemical extraction, and washing the fibre produced thereby to free it from soluble non-cellulose impurities.

"I. In the production of fibrous cellulose, the scutching, oi unretted fibre bearing vegetable stalks for the production of crude fibre, and the chemical digestion of the unhackled unretted crude fibre thus obtained for the chemical removal of non-cellulose impurities that are rendered soluble by chemical digestion.

8. In the production of fibrous cellulose, the scutching of unretted fibre bearing vegetable crude fibre, the digestion of the unhackled unretted crude fibre so obtained with a liquor containing caustic soda in excem of 12 degrees Baum for the chemical solution ,of non-fibrous impurities, said digestion being under pressure-with the exclusion ofair at a temperature in excess of 300 F.

9. In the preparation of fiax fibre, the scutching of unretted fiax straw for the mechanical removal of substantially 80% of the non-fibrous material and the digestion of crude fibre thus obtained in hot water at a temperature under 360 F., at a corresponding pressure greater than atmospheric and the hackling of the fibre thus obtained.

10. In the preparation of fiax fibre, thescutching of unretted flax strawfor the mechanical removal of the greater proportion of non-fibrous material to obtain a crude scutched fibre and the digestion of the crude scutched fibre thus obtained with hot water in a closed vessel at a temperature between 315 F. and 360 F. and at the'pressure corresponding therewith. 11. In the manufacture of fibre, the scutching of unretted fibre-bearing plant stalks for the 'mechanical removal oi the bulk of the nonfibrous material for the production of crude fibre, the digestion of the crude fibre thus obtained with'hot water in a closed vessel at a temperature under 360 Fpand under pressure above atmospheric in equilibrium therewith and the hackling of the fibre thus obtained.

12. In the preparation of fibre, the scutching of unretted fibre-bearing plant stalks for the production of scutched, unretted scrude fibre, the digestion of the scutched, unretted crude fibre thus obtained with a chemical in liquid condition consisting of a hot solution of sodic carbonate in a closed vessel at a temperature under'360" F. and under pressure in equilibrium therewith, the washing of the fibre thus obtained, and drying and hackllng.

13. Inthe manufacture of fibrous cellulose, the scutching' of unretted flax straw for the removal of substantially 80% or the non-fibrous material to obtain crude fibre, the digestion of the crude fibre so obtained with a chemical having a 'selective chemical digestive action on the non-cellulose matter remaining in the crude fibre and with the aid of heat and pressure to facilitate chemical extraction, and washing the fibre produced thereby to free it from soluble non-cellulose impurities and the employment in at least one wash water of a chemical of a non-acid character forming soluble salts with iron and other mineral compounds for the removal of mineral impurities.

14. In the production of cellulose fibre from the unretted stalks of best fibre plants, the scutchlng of the stalks to obtain crude fibre from which most of. the shives have been removed, and

the digestion of the unhackled unretted fibre thus obtained with substantially ten per centum caustic alkali liquor at a temperature of from 320 F. to 360 F. for the chemical removal of non-cellulose material including remaining as shives.

15. In the production of cellulose fibre from unretted fiax straw, the mechanical removal of seventy to seventy-five per centum thereof as non-fibrous material from substantially thirty to twenty-five per centum oi remalning crude fibre, the digestion of the unhacklecl unretted crude excess of eight per centum strength for three hours at a temperature in excess of 300 F. for the chemical removal of the remaining shives.

fibre thus obtained with caustic soda liquor in 16. In the production of cellulose fibre from the unretted straw of best fibre plants, the mechanical removal of most of the nonfibrous material from the cellulose fibre in the unretted straw, and the digestion of the unhackled unretted fibre thus obtained at a minimum temperature of about 320 F. for the chemical removal of the remaining shives.

'17. In the production of cellulose fibre from the straw of best fibre plants without retting, the

scutching of the unretted straw to separate the greater part of the shives from the cellulose fibre,

subjecting the unretted fibre thus obtained to the action of hot water to remove water-soluble material, freeing the fibre from said water and the material dissolved therein, and subjecting the fibre thus obtained to the action of a chemically acting shive dissolving liquid with the aid of heat and pressure to remove the remaining shives.

18. In the production of, paper from unretted fibre yielding fiax straw, scutching said straw unretted to obtain unretted scutched fibre with the greater part of the shives separated therefrom, subjecting the scutched unhackled fibre thus obtained to the chemically digesting action of. a degumming and deshiving liquid to chemically free the fibre from shives, washing the degummed and deshived fibre, bleaching the degummed and deshived fibre, pulping the bleached fibre, and forming paper from the pulp thus produced. I

19. In the production of paper from unretted fiax straw, scutching said unretted fiax straw to obtain unretted scutched fibre with the greater part of the non-fibrous material separated therefrom, subjecting the scutched unhackled fibre thus obtained to the chemically digesting action of a degumming and deshiving liquid at a minimum temperature of about 300 F., subjecting the degummed and deshived' fibre to a mild chlorine bleach, pulping the bleached fibre, and making the pulp thus formed into paper.

20. In the production of paper from unretted flax straw, scutching said unretted flax straw to cally digesting action of a degumming and deshiving liquid containing approximately ten per centum of caustic alkali, bleaching the d gummed and deshived fibre by use'of a mild chlorine bleach, pulping the bleached fibre, and making the resulting pulp into paper.

21. In the production of paper from unretted flax straw, scutching said unretted fiax straw to obtain scutched unretted fibre with the greater part of the shives separatedtherefrom, subjecting thescutched unhackled fibre to the action of hot water to remove from the fibre material including water soluble substances, subjecting the water-treated fibre to the solvent chemical action of an approximately ten per centum solution of caustic soda to degum and chemically deshive'the fibre, pulping the fibre and making the pulp into paper.

22. In the preparation of adapted for paper making, the scutching of flax straw toremove from thecellulose fibre thenein the greater part of the shives, the treatment of the scutched unhackled fibre thus obtained with hot water under pressure to remove material including water soluble matter, the treatment of the water-treated fibre with the solvent chemical action of a caustic soda solution at a minimum fibrous cellulose the unhackled soutched fibre for about three hours with a caustic soda solution at a minimum temperature of about 300 F. to degurn and chemically deshive the fibre, and the subjection of the fibre to a mild bleach, thereby preparing the fibre for pulping.

24. In the preparation of fiax fibre, the treatment of flax straw to produce a crude unhackled unretted fibre from which most of the shives have been removed and the digestion of said crude unretted fibre unhackled at a temperature of at least about 300 F. with a liquid to chemically 20 dissolve the non-cellulose impurities including the remaining shives.

' GEORGE A. LOWRY.

JIM A. GRANT. 

